This invention is directed to the field of elongated intraluminal devices having lubricious coatings, and, in particular, to a guidewire having a thin carbonaceous primer coat and a hydrophilic polymer top coat.
In a typical coronary procedure a guiding catheter having a preformed distal tip is percutaneously introduced into a patient""s peripheral artery, e.g. femoral or brachial artery, by means of a conventional Seldinger technique and advanced therein until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. There are two basic techniques for advancing a guidewire into the desired location within the patient""s coronary anatomy, the first is a preload technique which is used primarily for over-the-wire (OTW) devices and the bare wire technique which is used primarily for rail type systems. With the preload technique, a guidewire is positioned within an inner lumen of an OTW device such as a dilatation catheter or stent delivery catheter with the distal tip of the guidewire just proximal to the distal tip of the catheter and then both are advanced through the guiding catheter to the distal end thereof. The guidewire is first advanced out of the distal end of the guiding catheter into the patient""s coronary vasculature until the distal end of the guidewire crosses the arterial location where the interventional procedure is to be performed, e.g. a lesion to be dilated or a dilated region where a stent is to be deployed. The catheter, which is slidably mounted onto the guidewire, is advanced out of the guiding catheter into the patient""s coronary anatomy over the previously introduced guidewire until the operative portion of the intravascular device, e.g. the balloon of a dilatation or a stent delivery catheter, is properly positioned across the arterial location. Once the catheter is in position with the operative means located within the desired arterial location, the interventional procedure is performed. The catheter can then be removed from the patient over the guidewire. Usually, the guidewire is left in place for a period of time after the procedure is completed to ensure reaccess to the arterial location if it is necessary. For example, in the event of arterial blockage due to dissected lining collapse, a rapid exchange type perfusion balloon catheter such as described and claimed in U.S. Pat. No. 5,516,336 (McInnes et al.), can be advanced over the in-place guidewire so that the balloon can be inflated to open up the arterial passageway and allow blood to perfuse through the distal section of the catheter to a distal location until the dissection is reattached to the arterial wall by natural healing.
With the bare wire technique, the guidewire is first advanced by itself through the guiding catheter until the distal tip of the guidewire extends beyond the arterial location where the procedure is to be performed. Then a rail type catheter, such as described in U.S. Pat. No. 5,061,395 (Yock) and the previously discussed McInnes et al. which are incorporated herein by reference, is mounted onto the proximal portion of the guidewire which extends out of the proximal end of the guiding catheter which is outside of the patient. The catheter is advanced over the catheter, while the position of the guidewire is fixed, until the operative means on the rail type catheter is disposed within the arterial location where the procedure is to be performed. After the procedure the intravascular device may be withdrawn from the patient over the guidewire or the guidewire advanced further within the coronary anatomy for an additional procedure.
Conventional guidewires for angioplasty, stent delivery, atherectomy and other vascular procedures usually comprise an elongated core member with one or more tapered sections near the distal end thereof and a flexible body such as a helical coil or a tubular body of polymeric material disposed about the distal portion of the core member. A shapeable member, which may be the distal extremity of the core member or a separate shaping ribbon which is secured to the distal extremity of the core member extends through the flexible body and is secured to the distal end of the flexible body by soldering, brazing or welding which forms a rounded distal tip. Torquing means are provided on the proximal end of the core member to rotate, and thereby steer, the guidewire while it is being advanced through a patient""s vascular system.
Further details of guidewires, and devices associated therewith for various interventional procedures can be found in U.S. Pat. No. 4,748,986 (Morrison et al.); U.S. Pat. No. 4,538,622 (Samson et al.): U.S. Pat. No. 5,135,503 (Abrams); U.S. Pat. No. 5,341,818 (Abrams et al.); and U.S. Pat. No. 5,345,945 (Hodgson et al.) which are hereby incorporated herein in their entirety by reference thereto.
Guidewires have been the subject of continual improvement. One direction of improvement has centered on reducing the surface friction of the guidewire to facilitate relative movement between the guidewire and a guiding catheter or a dilatation catheter within a patient""s body lumen. Much of the innovation has centered on laminating low friction, polymeric materials onto the surface of the guidewire. However, it has proven difficult to obtain a tenacious bond between the lubricious polymer coating and the material of the guidewire. Further, achieving a uniform coat of polymer over the helical shapeable distal tip of most guidewires presents several difficulties. For example, bridging of the coat material between adjacent coils interferes with the designed flexibility of the distal tip and thereby effects performance of the guidewire.
In addition to guidewires, many intraluminal devices can benefit from a lubricious surface to facilitate insertion and guidance to the desired intraluminal destination. Reducing friction also minimizes luminal trauma caused by insertion of these devices, particularly in blood vessels such as coronary arteries. As with guidewires, much has been done with the prior art lubricious polymeric coatings to produce intraluminal devices having low friction surfaces. However, a number of drawbacks are associated with the use of polymeric coatings. Providing such devices with a uniform and tenacious coating is technically difficult and correspondingly expensive.
There remains a need for intraluminal devices having a lubricious polymeric coating which is thin and which is strongly adhered to the device. Further, there is a need for a process of applying such lubricious polymeric coatings in a repeatable, uniform and cost effective manner. This invention satisfies these and other needs.
This invention comprises an intraluminal device having a vapor deposited primer coat formed of a carbonaceous material and a lubricious top coat of a hydrophilic polymeric material. The invention also comprises the methods of making such intraluminal devices.
The vapor deposited primer coat of the invention may comprise substantially pure carbon, or a carbon-based material such as plasma polymerized hydrocarbons, polyurethane, or nylon, and preferably has a thickness of about 0.1 to about 2 xcexcm. A variety of carbonaceous source materials may be used to form the primer coat depending on the composition of the primer coat and the coating method used. The primer coat is applied to the surface of the intraluminal device using chemical vapor deposition (CVD), or in certain embodiments as discussed below, physical vapor deposition (PVD). The deposited primer coat forms an effective substrate for adhesion of a later applied hydrophilic polymer top coat. The hydrophilic polymer top coat may be applied by a variety of methods, including CVD, PVD, dipping, spraying and the like.
In a presently preferred embodiment of the invention, the primer coat and the hydrophilic top coat are applied to the surface of a distal tip coil of a guidewire. The use of vapor deposition provides a thin primer coat which provides uniform coverage of the helical coil. In a presently preferred embodiment of the invention, at least a stretched section of the coil are coated such that the adjacent turns of the coated coils do not touch one another. A thicker, less uniform primer coat would likely bridge the adjacent coils, or significantly increase the diameter of the coils so that bridging would likely result in the lubricious top coat, which can interfere with guidewire performance.
The deposited primer coat of the invention has superior adhesion to the base material of an intraluminal device, and provides improved adhesion between a hydrophilic top coat and the device. Additionally, the deposited primer coat does not bridge the adjacent turns of guidewire tip coils, and does not significantly increase the thickness of the coating on the device. These and other advantages of the invention will become more apparent from the following detailed description and accompanying exemplary drawings.